The present invention relates in general to automated-guided vehicles and methods for controlling an emergency stop thereof, and more particularly, to an automated-guided vehicle (hereinafter, xe2x80x9cAGVxe2x80x9d) having a switch to stop the AGV in emergency (hereinafter, xe2x80x9cemergency stop switchxe2x80x9d) and a method for controlling the emergency stop thereof.
Generally, an AGV automatically conveys an article by means of a motor and a controller such as a central processing unit (hereinafter, xe2x80x9cCPUxe2x80x9d) preprogrammed for an automatic operation.
The AGV is provided with an emergency stop switch to stop the AGV in emergency such as malfunction due to a short circuit, etc. If a user presses the emergency stop-switch, an emergency stop signal is inputted into the CPU, and the CPU interrupts a power supply to the driver to thereby stop an operation of the AGV. If the emergency stop switch is released, a release signal is transmitted to the CPU to thereby release the emergency stop of the AGV.
According to the conventional method to suspend the AGV in emergency, however, the emergency stop signal is transmitted to the CPU through an I/O circuit in the occurrence of emergency, and the CPU then issues a command of stopping the AGV. In this regard, if there is an emergency such as down of the CPU, etc., it is impossible to control an operation of the AGV. If the CPU is down while the AGV is in operation, the travelling path of the AGV cannot be determined, thus causing an emergency situation. Since the emergency stop is conducted by a software preprogrammed in the CPU according to the conventional emergency stop method, it is impossible to control an operation of the AGV, thereby being unable to stop the AGV.
Accordingly, the present invention has been made keeping in mind the above-described shortcoming, and an object of the present invention is to provide an AGV provided with an emergency stop switch which is used for stopping a driver of the, AGV where a CPU is down, and a method for controlling the emergency stop of the AGV.
This and other objects of the present invention may be achieved by a provision of an automated-guided vehicle having a driver, comprising an emergency stop switch for selecting an emergency stop and a release of the emergency stop of the driver; a state detector part for detecting a selection state of the emergency stop switch; and an emergency stop driving circuit for stopping in emergency an operation of the driver or releasing the emergency stop thereof according to a detection signal from the state detector part.
The automated-guided vehicle further comprises a delay circuit supplying an emergency stop signal from the state detector part to the emergency stop driving circuit, after delaying the signal for a predetermined time.
The delay circuit is comprised of a timer for adjusting the delay time.
The state detector part is comprised of a circuit for detecting the emergency stop signal and a circuit for detecting a release signal of the emergency stop.
The state detector part is comprised of at least one inverter converting each signal, a resistor and a capacitor for storing the converted signal therein and delaying the signal for the predetermined time, and a NAND gate into which the signal is inputted, outputting a pulse signal.
The emergency stop signal is converted by the inverter in the emergency stop signal detecting circuit; the converted signal is then divided, one divided signal being inputted into a first input port of the NAND gate passing through the inverter, and the other divided signal being converted by the inverter and inputted into the resistor and a storage circuit of the capacitor, and if the signal stored in the capacitor is entered into a second input port of the NAND gate after being inverted by the inverter, the on pulse signal is detected by outputting from the NAND gate, thereby driving the delay circuit.
The emergency stop signal detecting circuit is comprised of at least one inverter, a resistor, a capacitor, and a NAND gate.
The emergency stop release signal is divided in the emergency stop release signal detecting circuit; one divided signal is inputted into a first input port of the NAND gate; and the other divided signal is inputted into the resistor and a storage circuit of the capacitor through the inverter, and the signal stored in the capacitor is converted by the inverter and the inputted into a second input port of the NAND gate, the NAND gate outputs an off pulse signal according to the signals inputted thereinto; and the release of the emergency stop is conducted by the off pulse signal.
A method for controlling an emergency stop of an automated-guided vehicle having a driver, comprises the steps of selecting an emergency stop; detecting an emergency stop signal generated according to the selection of the emergency stop; activating an emergency stop driving circuit after delaying the emergency stop signal for a predetermined time; and turning off a power supply to the driver responsive to the activation of the emergency stop driving circuit.
The method further comprises the steps of releasing the emergency stop; and supplying the power to the driver responsive to the release of the emergency stop.